Encapsulation and delivery systems are important for many applications in consumer care and health care. A good encapsulation and delivery system should have 1) a good stability to achieve a long shelf life for storage and good integrity for drug delivery before reaching target sites, 2) stealth layers to provide a good dispersity in aqueous solution and targeting capability, and 3) a suitable fluidity for release of species encapsulated at target sites when needed. For some application, higher deposition efficiency is additionally required.
However, one the most formidable challenges in developing qualified encapsulation and delivery system is to address the dilemma between stability and fluidity of vesicles. A system with a good fluidity always has a poor stability. For example, liposomes obtained from self-assembly of amphiphilic lipids are dynamic and feasible for spices to move into and out, but the stability of liposomes are poor due to the weak interaction among short hydrophobic lipid segments which is responsible for the integrity of liposomes. Cross-linking or formation of polymer based or silica cages can stabilize liposomes but also reduce the fluidity. In comparison, the structures and properties of polymer vesicles formed by self-assembly of amphiphilic copolymers can be adjusted in a wider range through tuning the chemistry, composition and molecular weight of copolymers. Several polymeric formulations have been provided basically utilizing synthetic emulsifier such as polysorbate materials or glycerin fatty acid esters for delivery of dietary supplement Coenzyme 010. In addition, block copolymer of polyethylene glycol and poly propylene glycol have been applied for encapsulation and delivery of active ingredients. However, these systems cannot achieve the required balance between stability and fluidity.
In addition, should it be desired to deliver a fluidic active agent such as silicone oil to a site, the silicone oil is usually chemically altered to improve the deposition of the silicone oil. Silicone oil is usually used in hair products, fabric care and detergents. However, the chemical modification of the silicone oil may result in other undesired side effects such as sticky feeling and accumulation of the chemically modified silicone oil.
Therefore, it is attractive to develop stimuli-responsive encapsulation and delivery systems which can encapsulate the species securely, but also be able to release the species under stimuli which can be pH, thermal and redox etc, and without any undesirable side effects. Several types of pH responsive vesicles have been reported, such as pH-responsive PMAA-g-hollow silica vesicles and polymer complexes coated hollow silica vesicles. However, the formulations of these systems are not straightforward and can be cumbersome. In addition, the loading processes cannot be performed easily. In some cases, the loading of certain active ingredients cannot be realized or have a low loading efficiency and loading content. These limit the applications that can be used for such delivery systems.
There is a need to provide a core-shell particle that overcomes, or at least ameliorates, one or more of the disadvantages described above.